This application is based on, and claims priority to, Japanese Patent Application No. 2001-038201, filed Feb. 15, 2001, the entire contents of which are expressly incorporated by reference herein.
1. Field of the Invention
The present invention relates to small watercraft and, in particular, to an improved engine and component layout of a small watercraft which efficiently utilizes available space within an engine compartment of the watercraft hull.
2. Description of the Related Art
Personal watercraft have become very popular in recent years. This type of watercraft is quite sporting in nature and carries one or more riders. A relatively small hull of the personal watercraft defines a rider""s area above an engine compartment. An internal combustion engine powers a jet propulsion unit, which propels the watercraft. The engine lies within the engine compartment in front of a tunnel formed on an underside of the hull. The jet propulsion unit, which includes an impeller, is placed within the tunnel. The impeller has an impeller shaft driven by the engine. The impeller shaft usually extends between the engine and the jet propulsion device through a bulkhead of the hull tunnel.
Personal watercraft with four-cycle engines are now being produced primarily for reducing exhaust emissions. The four-cycle engine desirably includes a plenum chamber that has a relatively large volume so as to obtain high performance under all running conditions. The four-cycle engine, however, has two or more valves and a valve drive mechanism arranged to activate the valves. Such a large plenum chamber, multiple valves and a valve drive mechanism, as well as the foregoing throttle bodies, are factors which make the engine larger in height and/or width. On the other hand, because the rider""s area is defined above the engine compartment as noted above, the capacity and height of the engine compartment is limited. Otherwise, the seat position must be higher and/or wider which may not be comfortable for the rider.
Accordingly, it is important to make efficient use of the available space within the engine compartment defined by the hull of the watercraft so as to accommodate the necessary engine components within a hull sized to provide a comfortable seating position to the rider and any passengers. In addition, the overall center of gravity of the watercraft must be considered in the engine arrangement so as not to negatively affect the watercraft""s handling. Furthermore, with the limited access to the engine compartment, the engine and component arrangement preferably accommodates access to components of the engine which require routine maintenance.
One aspect of the present invention involves a small watercraft comprising a hull defining a vertically oriented, central longitudinal plane of the watercraft. The hull has an engine compartment with an internal combustion engine disposed therein. The engine has an engine body comprising a crankcase, a cylinder block and a cylinder head. The engine body includes at least one cylinder bore defining a cylinder axis. An air induction system is configured to guide air into a combustion chamber of the engine and comprises a plenum chamber. An exhaust system is provided for guiding exhaust gases from the combustion chamber to the atmosphere and comprises an exhaust conduit. The cylinder axis is canted with respect to the central plane and the exhaust conduit is disposed substantially on a side of the central plane to which the cylinder axis is canted. The plenum chamber is positioned on a side of the central plane opposite the exhaust conduit and extends substantially vertically from a position proximate the crankcase to a position proximate the cylinder head.
With such an arrangement, the available space within the engine compartment is advantageously utilized in an efficient manner. By canting the engine with respect to the central plane of the watercraft, the height of the engine is reduced, which allows the seat height of the watercraft to remain desirably low and provides a space above the engine for other components to be positioned. In addition, lowering the height of the engine lowers the overall center of gravity of the watercraft for improved handling. Further, by positioning the exhaust conduit on the side of central plane to which the engine is canted, a large amount of space is created on the opposite side of the engine. This space may be utilized to provide a relatively large plenum chamber for improved power output of the engine.
An additional aspect of the present invention involves a small watercraft comprising a hull including a pedestal for supporting a seat assembly. The hull additionally has an engine compartment with an internal combustion engine disposed therein. The engine has an engine body and an air induction system configured to guide air into a combustion chamber of the engine. The air induction system includes an air intake box defining a plenum chamber, which extends substantially vertically along a side of the engine body. A side of the air intake box facing the pedestal includes an access opening. The pedestal also includes a hull opening sized, shaped and positioned to permit access to the access opening of the air intake box.
Advantageously, such an arrangement permits convenient access to the plenum chamber, or interior, of the air intake box. Thus, components within the air intake box that may require service, such as the fuel injectors, throttle bodies, and especially the filter assembly. In addition, this arrangement permits the air intake box to be positioned beside the engine body and remain accessible. This provides flexibility in the engine and component layout which would not be possible if access to the engine compartment (and, thus, the air intake box) was available only through an upper opening in the hull below the seat assembly, as in many prior watercraft hull designs.
Another aspect of the present invention involves a small watercraft comprising a hull defining a vertically oriented, central longitudinal plane of the watercraft and including a pedestal for supporting a seat assembly. The hull additionally has an engine compartment and an internal combustion engine disposed therein. The engine has an engine body and an exhaust system for guiding exhaust gases from the combustion chamber to the atmosphere. The exhaust system includes an exhaust conduit having a portion passing along a side of the engine body. The pedestal includes a hull opening. At least a portion of the exhaust conduit protrudes outward through a plane defined by the hull opening. The hull additionally comprising a removable cover closing the hull opening, the cover being outwardly curved away from the pedestal to accommodate the exhaust conduit.
Such an arrangement advantageously permits additional space within the engine compartment to accommodate the exhaust conduit. In addition, the exhaust conduit may be made larger in cross sectional area to improve power output of the engine. The engine may also be canted at a greater angle than otherwise possible, to further lower the overall center of gravity of the watercraft. The opening in the hull also provides improved access to engine components within the engine compartment, including, for example, an oil filter of the engine.